Understand the source comparison
P21 Blood Work Labs Check Before After Comparison
Serum BDNF 10–30 ng/mL 15–30% ↑ 20–40% ↑ Confirms neurotrophin upregulation; flat BDNF suggests protocol failure or inflammatory block Most direct marker of P21 efficacy. If BDNF doesn't move, efficacy is questionable IGF-1 Age-adjusted normal Stable or modest
No winner is assigned.
This page preserves a source comparison for education. It does not add a rating, recommendation or clinical judgment.
- Serum BDNF
- 10–30 ng/mL
- 15–30% ↑
- 20–40% ↑
- Confirms neurotrophin upregulation; flat BDNF suggests protocol failure or inflammatory block
- Most direct marker of P21 efficacy. If BDNF doesn't move, efficacy is questionable
- IGF-1
- Age-adjusted normal
- Stable or modest ↑
- 10–20% ↑
- Reflects metabolic support for neurogenesis; not required but correlates with sustained effects
- Secondary marker. Useful context but not primary endpoint
- Hs-CRP
- <1.0 mg/L optimal
- ↓ toward <1.0 if elevated
- <1.0 mg/L
- Tracks systemic inflammation that can blunt peptide efficacy
- Elevated baseline hs-CRP is a major impediment. Address before starting P21
- Cortisol (AM fasting)
- 6–23 mcg/dL
- Stable or ↓ if high
- Mid-range 10–16 mcg/dL
- High baseline cortisol suppresses BDNF; normalization supports neuroplasticity
- Chronically elevated cortisol predicts poor response. Consider adaptogenic pre-treatment
- Liver enzymes (AST/ALT)
- <40 U/L
- Stable
- Monitors hepatic stress from peptide metabolism
- Elevation above 1.5× upper limit requires dose adjustment or discontinuation
- Triglycerides
- <150 mg/dL
- ↓ if elevated
- <100 mg/dL optimal
- Elevated triglycerides impair blood-brain barrier function and reduce peptide CNS penetration
- High baseline triglycerides suggest need for lipid optimization before P21